Analog Devices Inc. LTC1726IS8-5#TRPBF

Overview

LTC1726IS8-5#TRPBF from Analog Devices (formerly Linear Technology) is a triple supply monitor and microprocessor supervisory IC with adjustable reset timeout, adjustable watchdog timeout, and active-low open-drain RST output. It monitors 5V, 3.3V, and an adjustable input (VCCA), features ±1.5% threshold accuracy over temperature, 16µA typical supply current, and guarantees correct RST state down to VCC3 ≥ 1V or VCC5 ≥ 1V - used in desktop/notebook computers and network servers for reliable power-on reset and brownout protection.

For engineers reviewing the LTC1726IS8-5#TRPBF datasheet, LTC1726IS8-5#TRPBF pinout, LTC1726IS8-5#TRPBF application, or LTC1726IS8-5#TRPBF equivalent, key selection criteria include its triple-supply monitoring capability (5V/3.3V/ADJ), externally adjustable reset and watchdog periods via RT/WT capacitors, glitch-immune operation, and guaranteed reset assertion below 1V on monitored rails.

Technical Context

The LTC1726IS8-5#TRPBF integrates three independent voltage comparators with precision bandgap references, each monitoring VCC5 (4.675V nominal threshold), VCC3 (3.085V), and VCCA (1.000V), all specified at ±1.5% over –40°C to +85°C. Its reset and watchdog timers are capacitor-programmable using linear charge-current sources (1.4–2.6µA) driving RT and WT pins.

Reset assertion occurs when any monitored supply falls below its threshold; RST remains low until all supplies recover and the adjustable tRT delay expires. The watchdog timer resets the system if no WDI edge is detected within tWT, which restarts after each RST deassertion - enabling robust µP supervision in battery-powered and industrial embedded systems.

Key Specifications

Pinout & Package

Package: 8-Lead Plastic SO (S8), 0.150-inch narrow body, RoHS-compliant, rated for –40°C to +85°C operating temperature.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar triple-supply monitoring applications.

Compared with LTC1726IS8-5#TRPBF, LTC1727-5#TRPBF offers per-rail reset control at the cost of increased pin count and layout complexity, while LTC1326-5#TRPBF delivers superior threshold accuracy but sacrifices timing adjustability - making LTC1726IS8-5#TRPBF optimal for general-purpose, cost-sensitive, and timing-flexible designs.

Availability

LTC1726IS8-5#TRPBF is available at Aetrix Electronics and suitable for desktop computers, notebook computers, and network servers requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for LTC1726IS8-5#TRPBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Analog Devices acquired Linear Technology in 2017 and maintains its high-performance analog and power management portfolio with rigorous quality and longevity standards.

The LTC1726 series belongs to Linear's precision power supervision product line, designed specifically for reliable multi-rail monitoring and watchdog functionality in computing, communications, and instrumentation systems where deterministic reset behavior is mission-critical.

FAQ

What is the function of the VCCA pin on the LTC1726IS8-5#TRPBF?

The VCCA pin on the LTC1726IS8-5#TRPBF is a high-impedance 1V reference input used to monitor an adjustable supply voltage - typically configured via a resistor divider to sense voltages such as 1.2V, 1.8V, or 2.5V. It provides ±1.5% threshold accuracy over temperature and can be tied to VCC3 or VCC5 if unused. Its 1V nominal trip point enables supervision of low-voltage cores or analog supplies not covered by the fixed 5V/3.3V channels.

How do I calculate the reset timeout period for the LTC1726IS8-5#TRPBF?

The reset timeout period (tRT) for the LTC1726IS8-5#TRPBF is calculated as tRT = 3.30 × CRT, where CRT is the capacitance (in pF) connected between the RT pin and ground, and tRT is in microseconds. For example, a 47nF (47,000pF) capacitor yields tRT ≈ 155ms. Ceramic capacitors are recommended for low leakage. The LTC1726IS8-5#TRPBF datasheet specifies this linear relationship with ±30% variation over temperature for H-grade parts.

Can the LTC1726IS8-5#TRPBF monitor only two supplies instead of three?

Yes, the LTC1726IS8-5#TRPBF can be configured to monitor one or two supplies instead of three. For dual-supply operation, tie the unused VCCA pin to VCC3 or VCC5, or disable the VCC5 input by matching its voltage to VCC3 within ±25mV (for LTC1726-5 versions). The device will then supervise only the active inputs - for example, 5V and 3.3V - while maintaining full reset and watchdog functionality. This flexibility is documented in the Applications Information section of the LTC1726IS8-5#TRPBF datasheet.

What is the maximum supply voltage the LTC1726IS8-5#TRPBF can tolerate on its VCC5 pin?

The LTC1726IS8-5#TRPBF has an absolute maximum rating of 7V on the VCC5 pin, but its functional operating range is limited to 5V ±5% for accurate threshold detection. Exceeding approximately 4.15V activates the internal override circuit, causing the part to switch from 3.3V to 5V monitoring mode. Sustained operation above 5.25V risks violating the ±1.5% threshold specification and may affect long-term reliability - the LTC1726IS8-5#TRPBF is not rated for continuous 6V or higher operation.

Does the LTC1726IS8-5#TRPBF require external pull-up resistors on the RST pin?

The LTC1726IS8-5#TRPBF includes a weak internal pull-up (~6µA to VCC3), but external pull-up resistors are recommended when interfacing with 5V logic or when faster RST rise times are required. A 10kΩ resistor to VCC3 or VCC5 ensures VOH ≥ 4.5V under load, meeting TTL/CMOS input thresholds. The LTC1726IS8-5#TRPBF datasheet explicitly notes that external pull-ups improve performance in mixed-voltage systems and reduce susceptibility to noise on the RST line.